Automatic vehicular velocity control apparatus for automotive vehicle

ABSTRACT

In an automatic vehicular velocity control apparatus for an automotive vehicle, a relative velocity detector is provided to detect a relative velocity of a preceding vehicle to the vehicle, an inter-vehicle distance command value calculator is provided to calculate an inter-vehicle distance command value, a control response characteristic determinator is provided to determine a control response characteristic of the inter-vehicle distance control system according to a deviation from the inter-vehicle distance command value to a detected value of the inter-vehicle distance and a detected value of the relative velocity, a vehicular velocity command value calculator is provided to calculate a vehicular velocity command value on the basis of the determined control response characteristic of the inter-vehicle distance control system, and a vehicular velocity control section is provided to control at least one of a driving force of the vehicle, a braking force of the vehicle, and a gear ratio of a transmission in such a manner that a detected value of the vehicular velocity is made coincident with the vehicular velocity command value. The control response characteristic determinator includes maps representing a relationships of a specific angular frequency ω M  (or ωC) with respect to the relative velocity ΔV and an inter-vehicle distance deviation ΔL and a damping factor ζM (or ζc) with respect to the relative velocity and the inter-vehicle distance deviation.

BACKGROUND OF THE INVENTION

a) Field of the Invention

The present invention relates to an automatic vehicular velocity controlapparatus for an automotive vehicle to follow up a preceding vehiclewhich is running ahead of the vehicle at an appropriate inter-vehicledistance when the preceding vehicle has been recognized.

b) Description of the Related Art

A Japanese Patent Application First Publication No. Heisei 11-59222published on Mar. 12, 1999 exemplifies a previously proposed automaticvehicular velocity control apparatus to follow up a preceding vehiclewhich is running ahead of the vehicle at the same traffic lane at anappropriate inter-vehicle distance.

In the above-described control apparatus, a preceding vehicle follow-uprun control system is constituted by an inter-vehicle distance controlsystem and a vehicular velocity control system. A first gain fd by whichan inter-vehicle distance deviation ΔL is multiplied and a second gainfv by which a relative velocity ΔV of the vehicle to the precedingvehicle is multiplied are set on the basis of a specific angularfrequency ωM and a damping factor ζM in a transfer function of thepreceding vehicle follow-up run control system, a target relativevelocity V* is calculated as follows: ΔV*=(fd×ΔL+fv×ΔV), and a targetvehicular velocity V* is calculated by subtracting the target relativevelocity ΔV* from the vehicular velocity V_(T) of the preceding vehicle.

Then, if both of the first gain fd and the second gain fv are modifiedaccording to the detected value of the inter-vehicle distance, theresponse characteristic of the inter-vehicle distance control system ismodified.

SUMMARY OF THE INVENTION

However, since the response characteristic of the inter-vehicle distancecontrol system is-modified only by means of the detected value of theinter-vehicle distance, the following problems occur in the previouslyproposed automatic vehicular velocity control apparatus described in theBACKGROUND OF THE INVENTION.

(1) Suppose that the vehicle has recognized the preceding vehicle at aninter-vehicle distance sufficiently longer than a set inter-vehicledistance and is about to approach to the preceding vehicle whosevehicular velocity is lower than that of the vehicle up to the setinter-vehicle distance. An abrupt deceleration is, in this case, carriedout immediately after the preceding vehicle has been recognized evenwhen the relative velocity of the vehicle to the preceding vehicle islarge and the inter-vehicle distance when the preceding vehicle has justbeen recognized is sufficiently longer than the set inter-vehicledistance so that a vehicular run disagreeable to a vehicular occupant(s)occurs.

(2) Suppose that another vehicle has been interrupted into a spatialinterval of a traffic lane between the preceding vehicle and the vehicleduring the follow-up run of the vehicle to the preceding vehicle. Sincethe inter-vehicle distance between the other vehicle and the vehiclebecomes abruptly shorter than the set inter-vehicle distance, the abruptdeceleration is carried out immediately after the interruption of theother vehicle to the spatial interval between the old preceding vehicleand the vehicle although the relative velocity of the vehicle to theother interrupting vehicle is almost zero.

(3) Furthermore, suppose that the vehicle itself has made a traffic lanechange from a normal traffic lane on which the preceding vehicle wasrunning ahead of the vehicle to an overtake traffic lane on which anovertake vehicle is running ahead of the vehicle and the vehicle is tofollow up the overtake vehicle which is the new preceding vehicle.

If the inter-vehicle distance to the new preceding vehicle is shorterthan the set inter-vehicle distance, the abrupt deceleration of thevehicle is also carried out immediately after the follow-up run of thevehicle to the new preceding vehicle even if the vehicular velocity ofthe new preceding vehicle is higher than that of the vehicular velocityso that the vehicular run disagreeable to the vehicular occupant(s)occurs.

It is therefore an object of the present invention to provide animproved automatic vehicular velocity control apparatus for anautomotive vehicle which can achieve a smooth start for the vehicle toappropriately follow up a preceding vehicle which is running ahead ofthe vehicle with no driving anxiety given to the vehicular occupant(s)with an avoidance of the abrupt deceleration described above.

According to one aspect of the present invention, there is provided withan automatic vehicular velocity control apparatus for an automotivevehicle, comprising: an inter-vehicle distance detector to detect aninter-vehicle distance from the vehicle to a preceding vehicle which isrunning ahead of the vehicle; a vehicular velocity detector to detect avehicular velocity of the vehicle; a relative velocity detector todetect a relative velocity of the preceding vehicle to the vehicle; aninter-vehicle distance command value calculator to calculate a commandvalue of the inter-vehicle distance; a control response characteristicdeterminator to determine a control response characteristic of aninter-vehicle distance control system in accordance with to a deviationbetween the command value of the inter-vehicle distance and a detectedvalue thereof and a detected value of the relative velocity; a vehicularvelocity command value calculator to calculate a command value of thevehicular velocity on the basis of the determined control responsecharacteristic of the inter-vehicle distance control system; and avehicular velocity control section to control at least one of a drivingforce of the vehicle, a braking force of the vehicle, and a gear ratioof a vehicular transmission in such a manner that a detected value ofthe vehicular velocity is made equal to the command value of thevehicular velocity.

According to another aspect of the present invention, there is providedwith an automatic vehicular velocity control apparatus for an automotivevehicle, comprising: an inter-vehicle distance detector to detect aninter-vehicle distance from the vehicle to a preceding vehicle which isrunning ahead of the vehicle; a vehicular velocity detector to detect avehicular velocity of the vehicle; a relative velocity detector todetect a relative velocity of the preceding vehicle to the vehicle; aninter-vehicle distance command value calculator to calculate a commandvalue of an inter-vehicle distance; a target value determinator todetermine a target value of the inter-vehicle distance prescribing avariation of the inter-vehicle distance with time until the detectedvalue of the inter-vehicle distance has reached to the command value ofthe inter-vehicle distance; a gain determinator to determine a firstgain by which a deviation between the target value of the inter-vehicledistance and the detected value of the inter-vehicle distance ismultiplied in accordance with the detected value - of the relativevelocity; a vehicular velocity command value calculator to calculate acommand value of the vehicular velocity to make the detected value ofthe inter-vehicle distance equal to the target value of theinter-vehicle distance on the basis of the detected value of thevehicular velocity, the detected value of the relative velocity, and thedeviation between the target value of the inter-vehicle distance and thedetected value thereof; and a vehicular velocity control section tocontrol at least one of a driving force of the vehicle, a braking forceof the vehicle, and a gear ratio of a vehicular transmission in such amanner that the detected value of the vehicular velocity is made equalto the command value thereof.

This summary of the invention does not necessarily describe allnecessary features so that the present invention may also be asub-combination of these described features.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a block diagram of an automatic vehicular velocity controlapparatus for an automotive vehicle in a first preferred embodimentaccording to the present invention.

FIG. 1B is a circuit block diagram of a controller shown in FIG. 1A.

FIG. 2 is a functional block diagram of the automatic vehicular velocitycontrol apparatus shown in FIG. 1A.

FIG. 3 is a functional block diagram of the automatic vehicular velocitycontrol apparatus in a second preferred embodiment according to thepresent invention.

FIG. 4 is a functional block diagram of a vehicular velocity controlsystem in the automatic vehicular velocity control apparatus applicableto each embodiment.

FIGS. 5A, 5B, and 5C are simulation results in an inter-vehicledistance, a relative velocity, and an acceleration of a comparativeexample of the automatic vehicular velocity control apparatus when thevehicle is approaching to a preceding vehicle at a relatively longinter-vehicle distance as shown in FIG. 11.

FIGS. 6A, 6B, and 6C are simulation results in the inter-vehicledistance, the relative velocity, the acceleration of the automaticvehicular velocity control apparatus in each of the first and secondembodiments when the vehicle is approaching to the preceding vehicle inthe same situation as shown in FIG. 11.

FIGS. 7A, 7B, and 7C are simulation results in the inter-vehicledistance, the relative velocity, and the acceleration of the comparativeexample of the automatic vehicular velocity control apparatus whenanother vehicle is interrupted into a spatial interval between thepreceding vehicle and the vehicle in the same situation as shown in FIG.12.

FIGS. 8A, 8B, and 8C are simulation results in the inter-vehicledistance, the relative velocity, and the acceleration of the automaticvehicular velocity control apparatus in each of the first and secondembodiments when the other vehicle is interrupted into the spatialinterval between the preceding vehicle and the vehicle in the samesituation as shown in FIG. 12.

FIGS. 9A, 9B, and 9C are simulation results in the inter-vehicledistance, the relative velocity, and the acceleration of the comparativeexample of the automatic vehicular velocity control apparatus in each ofthe first and second embodiments when the vehicle has made a trafficlane change to an overtake traffic lane at which the vehicle is runningto follow up an overtake vehicle as a new preceding vehicle in the samesituation as shown in FIG. 13.

FIGS. 10A, 10B, and 10C are simulation results in the inter-vehicledistance, the relative velocity, and the acceleration of the automaticvehicular velocity control apparatus when the vehicle has made thetraffic lane change to the overtake traffic lane at which the vehicle isrunning to follow up the overtake vehicle as the new preceding vehiclein the same situation as shown in FIG. 13.

FIG. 11 is an explanatory view for explaining one of the variousfollow-up run situations in which the vehicle is approaching to thepreceding vehicle.

FIG. 12 is an explanatory view for explaining one of the variousfollow-up run situations in which the other vehicle is interrupted intothe traffic lane on which the vehicle is running.

FIG. 13 is an explanatory view for explaining one of the variousfollow-up run situations in which the vehicle has made the traffic lanechange to the overtake traffic lane to follow up the overtake vehicle.

FIG. 14 is a functional block diagram of the automatic vehicularvelocity control apparatus in a third preferred embodiment according tothe present invention.

FIG. 15 is an example of a map representing a specific angular frequencyωc of an inter-vehicle distance control system with respect to arelative velocity in the third embodiment shown in FIG. 14.

FIG. 16 is an example of a map representing a damping factor ζc of theinter-vehicle distance control system with respect to the relativevelocity in the third embodiment shown in FIG. 14.

FIG. 17A is a functional block diagram of the automatic vehicularvelocity control apparatus in a fourth preferred embodiment of theautomatic vehicular velocity control apparatus according to the presentinvention.

FIG. 17B is a functional block- diagram of the inter-vehicle distancecontrol system and the vehicular velocity control system of theautomatic vehicular velocity control apparatus as an alternative of thefourth preferred embodiment of the automatic vehicular velocity controlapparatus according to the present invention.

FIGS. 18A, 18B, 18C, and 18D are graphs on simulation results of theinter-vehicle distance, the vehicular velocity, the relative velocity,and the acceleration of the automatic vehicular velocity controlapparatus in each of the first and second embodiments when the specificangular frequency in the inter-vehicle distance control system is madehigh.

FIGS. 19A, 19B, 19C, and 19D are graphs on the simulation results of theinter-vehicle distance, the vehicular velocity, the relative velocity,and the acceleration of the automatic vehicular velocity controlapparatus in each of the first and second embodiments when the specificangular frequency in the inter-vehicle distance control system is madelow and the vehicle is following up the preceding vehicle, with therelative velocity being high.

FIGS. 20A, 20B, 20C, and 20D are graphs on the simulation results of theinter-vehicle distance, the vehicular velocity, the relative velocity,and the acceleration of the automatic vehicular control apparatus ineach of the third and fourth preferred embodiments when the vehicle isfollowing up the preceding vehicle, with the relative velocity beinghigh.

FIGS. 21A, 21B, 21C, and 21D are graphs on the simulation results of theinter-vehicle distance, the vehicular velocity, the relative velocity,and the acceleration of the automatic vehicular control apparatus ineach of the third and fourth preferred embodiments when the vehicle isfollowing up the preceding vehicle, with the relative velocity beinghigh.

FIGS. 22A, 22B, 22C, and 22D are graphs on the simulation results of theinter-vehicle distance, the vehicular velocity, the relative velocity,and the acceleration of the automatic vehicular control apparatus ineach of the first and second preferred embodiments when the vehicle isfollowing up the preceding vehicle, with the relative velocity beinglow.

FIGS. 23A, 23B, 23C, and 23D are graphs on the simulation results of theinter-vehicle distance, the vehicular velocity, the relative velocity,and the acceleration of the automatic vehicular control apparatus ineach of the third and fourth preferred embodiments when the vehicle isfollowing up the preceding vehicle, with the relative velocity beinglow.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will hereinafter be made to the drawings in order tofacilitate a better understanding of the present invention.

(First Embodiment)

FIG. 1A shows a whole configuration of an automatic vehicular velocitycontrol apparatus in a first preferred embodiment according to thepresent invention applicable to an automotive vehicle.

In FIG. 1A, an inter-vehicle distance sensor 1 is disposed on a frontlower portion of the vehicle to detect an inter-vehicle distance fromthe vehicle to a preceding vehicle which is running ahead of the vehicleon the same traffic lane as the vehicle.

The inter-vehicle distance sensor 1 is constituted by, for example, aradar unit which emits a laser light beam toward a front detectable zoneand receives a reflected light beam from an object present in the frontdetectable zone.

The inter-vehicle distance L to the preceding vehicle and a relativevelocity ΔV of the vehicle to the preceding vehicle are detected.

The relative velocity ΔV is derived by differentiating the detectedvalue L of the inter-vehicle distance or may be derived by passing thedetected value L of the inter-vehicle distance through a band passfilter (BPF).

It is noted that the inter-vehicle distance may be detected using anelectromagnetic wave or an ultrasonic wave and the relative velocity maybe calculated from the detected result through such a medium as theelectromagnetic wave or the ultrasonic wave.

A vehicular velocity sensor 2 detects a revolution velocity of an outputaxle of a transmission 4 to be converted to a vehicular velocity V.

A controller 5 (also called, a preceding vehicle follow-up runcontroller) includes a microcomputer and its peripheral devices. Themicrocomputer includes, as shown in FIG. 1B, a CPU (Central ProcessingUnit and specifically aMPU (microprocessor unit)), a RAM (Random AccessMemory), a ROM (Read Only Memory), an Input Port, an Output Port, and acommon bus.

The controller 5 calculates a vehicular velocity command value V* suchthat both of the inter-vehicle distance L and the relative velocity ΔVgive their optimum values on the basis of the inter-vehicle distance L,the relative velocity ΔV, and the vehicular velocity V when the vehiclefollows up the preceding vehicle. The details of the controller 5 willbe described later.

A vehicular velocity control section 4 calculates a plurality of commandvalues to command an engine throttle valve actuator to open an enginethrottle valve 3, a command value to command an automatic bake actuator60 to generate a braking liquid pressure in a brake system 6 accordingto its command value, and a command value to command a gear ratioactuator 40 to adjust the gear ratio of the transmission 4(5) accordingto its command value.

The vehicular velocity control section 4(5) is shown in FIG. 2.

A feedback control technique or a robust model matching technique isapplicable to the vehicular velocity control section 4(5).

For example, a Japanese Patent Application First Publication No. Heisei10-272963 published on Oct. 13, 1998 exemplifies the robust modelmatching technique applied to the vehicular velocity control section4(5).

The throttle valve actuator 30 adjustably derives the opening angle ofthe engine throttle valve 3 according to the command value of the enginethrottle valve 3.

The automatic brake actuator 60 adjusts the braking liquid pressure ofthe brake system 6 according to its command value. The transmission gearratio actuator 40 adjusts the gear ratio of the transmission 4 a.Although the transmission 4 a is an automatic transmission in the firstembodiment, the transmission 4 a may be a continuously variabletransmission (CVT). In the case of the continuously variabletransmission, the gear ratio means a speed ratio.

In the first embodiment shown in FIGS. 1A, 1B, and 2, a transferfunction Gv(s) of a vehicular velocity control system to which thevehicular velocity command value V* from the preceding vehicle follow-uprun control system 50(5) of the controller 5 is inputted and from whichthe vehicular velocity V detected by means of the vehicular velocitysensor 2 is outputted is approximated to such a first-order lag systemas expressed in an equation (1) of TABLE 3.

In the equation (1), ωv denotes a break point angular frequency of thetransfer function of the vehicular velocity control system (ωv=1/T, Tdenotes a time constant).

As shown in FIG. 2, the preceding vehicle follow-up run controller 50(5)functionally includes, in terms of a software configuration of themicrocomputer, an inter-vehicle distance command value calculatingsection 501, a coefficients determining section 502, a targetinter-vehicle distance calculating section 503, and a vehicular velocitycommand value calculating section 504.

The preceding vehicle follow-up run control system 50 receives theinter-vehicle distance L and the relative velocity ΔV from theinter-vehicle distance sensor 1 and the vehicular velocity V from thevehicular velocity sensor 2.

It is noted that in a case where the preceding vehicle is not in thefront detectable zone of the inter-vehicle distance sensor 1, thepreceding vehicle follow-up run control system 50(5) outputs a vehicularvelocity set by a vehicular occupant (a set vehicular velocity) to thevehicular velocity control section 4 as the vehicular velocity commandvalue V* so that the vehicle runs constantly at the set vehicularvelocity (cruise run).

On the other hand, if the inter-vehicle distance sensor 1 recognizes thepresence of the preceding vehicle in the front detectable zone, theinter-vehicle distance command value calculating section 501 calculatesthe inter-vehicle distance command value L* on the basis of thevehicular velocity V and the relative velocity ΔV.

The vehicular velocity V_(T) of the preceding vehicle is expressed asfollows:

V_(T)=V+ΔV  (2).

The command value L* of the inter-vehicle distance is calculated as thefunction of the vehicular velocity of the preceding vehicle.

That is to say, $\begin{matrix}\begin{matrix}{L^{*} = {{a \cdot V_{T}} + {Lof}}} \\{= {{a \cdot \left( {V + {\Delta \quad V}} \right)} + {{Lof}.}}}\end{matrix} & (3)\end{matrix}$

In the equation (3), a denotes a coefficient and Lof denotes an offset.

Alternatively, the command value L* of the inter-vehicle distance may becalculated as a function of the vehicular velocity V.

L*=a′·V+Lof′  (4).

In the equation (4), a′ denotes another coefficient and Lof′ denotesanother offset.

Furthermore, the set vehicular velocity by the vehicular occupant(s) maybe used as the command value of the inter-vehicle distance L*.

The coefficients determining section 502 determines the damping factorζM and the specific angular frequency ωM in the inter-vehicle distancecontrol system according to the inter-vehicle distance deviation ΔL andthe relative velocity ΔV in order to provide an optimum responsecharacteristic according to the inter-vehicle distance deviation ΔL andthe relative velocity ΔV for the response characteristic of theinter-vehicle distance control system until the actual inter-vehicledistance L has reached in the command value L* of the inter-vehicledistance in the inter-vehicle distance control system from which theinter-vehicle distance command value L* from the inter-vehicle distancecommand value calculating section 301 is inputted and from which theactual inter-vehicle distance detected by means of the inter-vehicledistance sensor 1 is outputted.

It is noted that the inter-vehicle distance deviation

ΔL is expressed as ΔL=L−L*   (5).

Specifically, numerical values of the damping factor ζM and the specificangular frequency ωM in the inter-vehicle distance control system arepreviously set (stored) as respective maps in accordance with theinter-vehicle distance deviation ΔL and the relative velocity ΔV inorder to obtain the optimum response characteristic on the inter-vehicledistance control in various follow-up run situations and determines thedamping factor ζM and the specific angular frequency ωM in theinter-vehicle distance control system are previously stored (set) asrespective maps in accordance with the inter-vehicle distance deviationΔL and the relative velocity ΔV in order to obtain the optimum responsecharacteristic on the inter-vehicle distance control system in variousfollow-up run situations and determines the values of coefficients ofthe damping factor ζM and the specific angular frequency of ωM inaccordance with the inter-vehicle distance deviation ΔL and the relativevelocity ΔV for a target inter-vehicle distance calculation.

TABLE 1 shows an example of the map on the damping factor of ζM andTABLE 2 shows an example of the other map on the specific angularfrequency of ωM.

The target inter-vehicle distance calculating section 501 calculates atarget inter-vehicle distance L_(T) and a target relative velocityΔV_(T) through a second order filter described in an equation (6) ofTABLE 3 using the damping factor ζM and the specific angular frequencyω_(M) to provide a target response characteristic in the inter-vehicledistance control system for the response characteristic. It is notedthat the inter-vehicle distance L0 and the relative velocity V0immediately after the preceding vehicle has been recognized are set totheir initial values.

The target inter-vehicle distance L_(T) and the target relative velocityΔV_(T) are a final inter-vehicle distance command value prescribing atime transition of the inter-vehicle distance and the relative velocityso that the actual inter-vehicle distance exhibits the target responsecharacteristic and is converged into the inter-vehicle distance commandvalue L*.

If the equation (6) is evolved and a Laplace transform is carried outfor the evolved equation (6), an equation (7) of TABLE 3 can be given.

The equation (7) represents a transfer function of the targetinter-vehicle distance L_(T) to the inter-vehicle distance command valueL* and is expressed in the second-order form.

In the first embodiment, a feedback control is carried out in theinter-vehicle distance control system so that the actual inter-vehicledistance L provides the target inter-vehicle distance L_(T) (finalinter-vehicle distance command value) represented by the equation (7).

As described above, since the values such that the target inter-vehicledistance control response can be obtained in accordance with theinter-vehicle distance deviation ΔL and the relative velocity ΔV are setfor the damping factor ζM and the specific angular frequency ωM in theinter-vehicle distance control system, a desirable inter-vehicledistance control response can be achieved under various follow-up runsituations.

Such a response characteristic that the actual inter-vehicle distance isslowly converged into the command value without abrupt deceleration ofthe vehicle is desirable as the target inter-vehicle control responsecharacteristic is a case where the relative velocity to the precedingvehicle is low (small) even with the inter-vehicle distance to thepreceding vehicle being shorter than the command value thereof whenanother vehicle (a new preceding vehicle) is interrupted into a spatialinterval between the preceding vehicle (the old preceding vehicle) andthe vehicle or when the vehicle has made a traffic lane change to anovertake traffic lane on which the overtake vehicle is present as thenew preceding vehicle.

In addition, such a response characteristic that the actualinter-vehicle distance is slowly converged to the command value thereofwithout the abrupt deceleration in a case where the relative velocity islarge (high) with the inter-vehicle distance being long when the vehicleis approaching to the new preceding vehicle.

In such the follow-up run control situations as described above, theactual inter-vehicle distance overshoots or undershoots around thecommand value thereof and converges to the command value thereof toexhibit the second-order response characteristic. Such the second-orderresponse characteristic can be achieved through the second-order filtershown in the equations (6) and (7).

The vehicular velocity command value calculating section 504 calculatesthe command value L* of the vehicular velocity using predetermined(gain) constants fv and f_(L) in accordance with the following equation(8).

V*={V(t)+ΔV(t)}−[fv{ΔV_(T)(t)−ΔV(t)}+f_(L){L_(T)(t)−L(t)}]  (8).

In the equation (8), fv denotes a first gain constant by which a targetrelative velocity deviation (a difference from a target relativevelocity ΔV_(T)(t) to a detected value of the relative velocity ΔV(t))is multiplied and f_(L) denotes a second gain constant by which a targetinter-vehicle distance deviation (a difference from a targetinter-vehicle distance L_(T)(t) to the detected value L(t) of theinter-vehicle distance) {L_(T)(t)−L(t)} is multiplied.

The vehicular velocity control section 4 adjusts at least one or each ofthe throttle valve actuator 30, the automatic brake actuator 10, and A/Tgear ratio actuator 40 to make the actual vehicular velocity V(t) equalto the command value V* of the vehicular velocity.

(Second Embodiment)

In the first embodiment, the feedback control is exemplified to make theactual inter-vehicle distance L equal to the target inter-vehicledistance L_(T) indicating the target response characteristic of theinter-vehicle distance. However, in this inter-vehicle distance feedbackcontrol system, a control gain in the inter-vehicle distance controlsystem needs to be increased with a control time constant thereof beingshortened in order to increase the response characteristic. At thistime, a control stability is sacrificed and there is a trade-offrelationship between the response characteristic (speed of response) andthe stability of control.

In a second preferred embodiment, a feed-forward loop is added to theinter-vehicle distance feedback control system in the first embodimentto derive a compensated vehicular velocity command value Vc to achievethe target inter-vehicle distance response from the command value L* ofthe inter-vehicle distance. This compensated vehicular velocity commandvalue Vc corrects the vehicular velocity command value V* derived in theinter-vehicle distance control system according to the command value Vcof the compensated vehicular velocity. Consequently, the controlresponse characteristic can be improved without sacrifice of thestability in the inter-vehicle distance control.

FIG. 3 shows the functional block diagram of the controller 5 in thesecond embodiment.

The preceding vehicle follow-up run controller 50(5) includes apre-compensation vehicular velocity command value calculating section505 connected to the input end of the target inter-vehicle distancecalculating section 503 and a corrected vehicular velocity command valuecalculating section 506 in addition to the inter-vehicle distancecommand value calculating section 501, the coefficients determiningsection 502, the target inter-vehicle distance calculating section 503,and the vehicular velocity command value calculating section 504.

The pre-compensation vehicular velocity command value calculatingsection 505 calculates the compensated vehicular velocity command valueVc from the command value L* of the inter-vehicle distance through afilter expressed in an equation (9) of TABLE 3.

The filter in the equation (9) is represented by a product between aninverse of the transfer function from the vehicular velocity commandvalue V* to the actual inter-vehicle distance L and the control responsecharacteristic of the target inter-vehicle distance shown in theequation (7). It is noted that the transfer function from the vehicularvelocity command value V* to the actual inter-vehicle distance L isrepresented by a product between the transfer function of the vehicularvelocity control system having the input of the vehicular velocitycommand value V* and the output of the actual vehicular velocity V (theequation (1)) and a deviation between the actual vehicular velocity Vand the vehicular velocity V_(T) of the preceding vehicle, i.e., anintegrator to integrate the relative velocity ΔV to derive the actualinter-vehicle distance L, as shown in FIG. 4. Initial values whencalculating the compensated vehicular velocity command value Vccorresponding to the equation (9) of TABLE 3 are the inter-vehicledistance L0 and the relative velocity ΔV0 which are derived immediatelyafter the inter-vehicle distance sensor 1 has just been recognized thepresence of the preceding vehicle.

V*′=V*+Vc  (10).

Then, the vehicular velocity control section 4 controls at least one oreach of the throttle valve actuator 30, the automatic brake actuator 60,and the A/T gear ratio actuator 40 to make the actual vehicular velocityV equal to the vehicular velocity command value V*′.

FIGS. 5A through 10C show the results of simulations.

It is noted that since the results of simulations in the firstembodiment indicate the same results of simulations in the secondembodiment (as will be described later), the explanations of the case ofthe first embodiment will be omitted herein.

FIGS. 5A, 5B, and 5C show timing charts indicating the inter-vehicledistance, the relative velocity, and the acceleration (a signedacceleration, namely, a variation rate of the vehicular velocity) when acomparative example of the automatic vehicular velocity controlapparatus in each of the first and second embodiments is operated in acase where the vehicle has recognized the presence of the precedingvehicle and thereafter approached to the preceding vehicle up to the set(target) inter-vehicle distance as shown in FIG. 11.

FIGS. 6A, 6B, and 6C show timing charts indicating the inter-vehicledistance, the relative velocity, and the acceleration when the automaticvehicular velocity control apparatus in the second embodiment isoperated in the same case shown in FIG. 11.

In each of FIGS. 5A through 6C, each solid line denotes a case of thevehicular velocity of 100 Km/h, the initial value of the inter-vehicledistance of 100 m, and the vehicular velocity of the preceding vehicleof 75 Km/h, the initial value of the inter-vehicle distance of 100 m,and the vehicular velocity of the preceding vehicle of 90 Km/h.

Since, in the comparative example, in a case where the relative velocityof the vehicle to the preceding vehicle is large, the abruptdeceleration is carried out immediately after the preceding vehicle hasbeen recognized as shown in the solid line even when the inter-vehicledistance is long, a negatively large acceleration (deceleration) occursin the vehicle so that the vehicular run disagreeable to the vehicularoccupant occurs.

However, since, in the second embodiment, when the actual inter-vehicledistance is longer than the command value thereof and the inter-vehicledistance deviation is large although the relative velocity value to thepreceding vehicle is large, such the damping factor and the specificangular frequency as to provide the inter-vehicle distance controlresponse which is slowly converged to the command value of theinter-vehicle distance can be provided by the previously set mapsthereon, the vehicle tends to be too approached to the preceding vehicleto some degree but a degree of decrease in the relative velocity becomesmoderate. However, the large deceleration is not generated but a smoothstart to follow up the preceding vehicle can be achieved without givingthe vehicular run disagreeable to the vehicular occupant(s). It is notedthat in a case where the relative velocity to the preceding vehicle isreduced, the similar simulation results as the comparative example areobtained.

FIGS. 7A, 7B, and 7C show timing charts of the inter-vehicle distance,the relative velocity, and the acceleration of the comparative exampleas the results of simulations when the other vehicle which has runningat a different traffic lane is interrupted into the traffic lane beforethe vehicle as the new preceding vehicle as shown in FIG. 12.

FIGS. 8A, 8B, and 8C show timing charts of the inter-vehicle distance,the relative velocity, and the acceleration of the automatic vehicularvelocity control apparatus in the second embodiment as the results ofsimulations in the same situation as shown in FIG. 12.

It is noted that the vehicular velocities of the vehicle and of thepreceding vehicle were 90 Km/h and the vehicular velocity of theinterrupted new preceding vehicle was 30 m. Each solid line in FIGS. 7A,7B, and 7C denotes the actual response and each broken line thereindenotes the target response.

In the comparative example, when the inter-vehicle distance between thevehicle and the interrupt new preceding vehicle became abruptly short,the abrupt deceleration of the vehicle was carried out immediately afterthe vehicular interruption occurred, and the large deceleration of thevehicle was developed even if the relative velocity value to theinterrupt new preceding vehicle was small so that the vehicular rundisagreeable to the vehicular occupant occurred.

In the second embodiment, however, since such the damping factor and thespecific angular frequency as to provide the control response of theinter-vehicle distance which is slowly converged into the command valueof the inter-vehicle distance by the previously set maps, the vehicletends to be approached to the new preceding vehicle to some degree butthe degree of decrease in the relative velocity became moderate. Inaddition, no large deceleration occurs and the smooth start to follow upthe interrupt new preceding vehicle can be achieved without giving thedisagreeable vehicular run to the vehicular occupant(s).

FIGS. 9A, 9B, and 9C show timing charts representing the inter-vehicledistance, the relative velocity, and the acceleration of the case of thecomparative example as the results of simulations when the vehicle hasmade the traffic lane change after the overtake vehicle as the newpreceding vehicle to the adjacent overtaking traffic lane to overtakethe preceding vehicle (old preceding vehicle) as shown in FIG. 13.

FIGS. 10A, 10B, and 10C show timing charts representing theinter-vehicle distance, the relative velocity, and the acceleration ofthe automatic vehicular velocity control apparatus in the secondembodiment as the results of simulations in the same situation as shownin FIG. 13.

It is noted that the vehicular velocity of the vehicle and the vehicularvelocity of the preceding vehicle were 75 Km/h, the vehicular velocityof the new preceding vehicle which is running at the overtake trafficlane was 90 Km/h, and the inter-vehicle distance from the vehicle to thepreceding vehicle immediately after the vehicle has entered the overtaketraffic lane was 20 m.

In the comparative example, when the vehicle has made the traffic lanechange to the adjacent lane before the overtaking vehicle and theinter-vehicle distance to the overtaking vehicle as the new precedingvehicle becomes abruptly short, the abrupt deceleration of the vehiclewas carried out even if the relative velocity to the overtake vehicle issmall (low). Then, the large deceleration of the vehicle occurs so as togive the vehicular occupant(s) the disagreeable vehicular run.

However, in the second embodiment, since in a case where the relativevelocity is small even when the actual inter-vehicle distance is shorterthan the command value of the inter-vehicle distance and the deviationof the inter-vehicle distance indicates negative, such the dampingfactor and the specific angular frequency as to provide the controlresponse characteristic as to be slowly converged into the command valueof the inter-vehicle distance by means of the retrieved previously setmap data, the vehicle tended to be approached to the new precedingvehicle but the degree of decrease in the relative velocity becamemoderate. Then, no large deceleration occurred and the smooth start tofollow up the (new) preceding vehicle can be achieved without giving thedisagreeable vehicular run to the vehicular occupant(s).

As described hereinabove, in each of the first and second embodiments,the damping factor and the specific angular frequency in theinter-vehicle distance control system are previously stored as the maps(TABLE 1 and TABLE 2) in accordance with the inter-vehicle distancedeviation and the relative velocity so as to provide the optimuminter-vehicle distance control in various follow-up run situations asshown in FIGS. 11 through 13. Then, the command value of the vehicularvelocity based on the target inter-vehicle distance and the targetrelative velocity is calculated and the driving force, the brakingforce, and/or the gear ratio of the transmission 4 is controlled inaccordance with the command value of the vehicular velocity. Hence, invarious follow-up run situations, the optimum inter-vehicle distancecontrol response can be achieved and the smooth follow-up run to thepreceding vehicle can be started without the abrupt deceleration.

In addition, in the second embodiment, the response characteristic canbe improved without sacrifice of the stability in the inter-vehicledistance control system.

In the second embodiment, the follow-up run control according to thepresent invention is applicable to the various follow-up run situationsshown in FIGS. 11, 12, and 13.

However, the follow-up run control according to the present invention isapplicable to the other situations than those shown in FIGS. 11 to 13.

It is noted that the hardware structure of the second embodiment is thesame as in the first embodiment shown in FIGS. 1A and 1B.

(Third Embodiment)

In each of the first and second preferred embodiments, the dampingfactor ζ_(M) and ω_(M) to determine the response characteristic of thetarget inter-vehicle distance L_(T) are set in accordance with theinter-vehicle distance deviation (L-L*) and the relative velocity ΔV. Ina third embodiment of the automatic vehicular velocity control apparatusaccording to the present invention, the predetermined constants fv andfL (refer to the equation (8) described above) in the inter-vehicledistance feedback control system are set in accordance with the relativevelocity ΔV(t) to make the actual inter-vehicle distance L(t) equal tothe target inter-vehicle distance L_(T)(t). Then, the responsecharacteristic in the inter-vehicle distance control system can beimproved.

It is noted that the constants fv and fL in the inter-vehicle distancefeedback control system are called gains, the gain fL by which thedifference between the target inter-vehicle distance L_(T)(t) and theactual inter-vehicle distance L(t), namely, the target inter-vehicledistance deviation {L_(T)(t)−L(t)} is multiplied is called the firstgain and the gain fv by which the difference between the target relativevelocity ΔV(t) and the actual relative velocity ΔV(t), namely, thetarget relative velocity deviation {ΔV_(T)(t)−ΔV(t)} is multiplied iscalled the second gain.

In the situation wherein the vehicle follow-up the preceding vehiclewhose relative velocity value to the vehicle is small (low) as shown inFIGS. 12 and 13, the vehicle is decelerated with the large degree ofdeceleration, increasing a follow-up capability of the actualinter-vehicle distance L(t) to the target inter-vehicle distanceL_(T)(t).

At this time, the vehicular run disagreeable to the vehicularoccupant(s) is given. It is, however in this case, desirable to widenthe inter-vehicle distance but to slowly decrease the vehicularvelocity. To achieve this, it is necessary to reduce the first gain fLby which the target inter-vehicle distance deviation in theinter-vehicle distance feedback control system {L_(T)(t)−L(t)} ismultiplied and to increase the second gain fv by which the targetrelative velocity deviation {ΔV_(T)(t)−ΔV(t)} is multiplied. Hence, theresponse characteristic of the inter-vehicle distance feedback controlsystem becomes slow.

On the other hand, in such a follow-up run situation as to follow up thepreceding vehicle whose relative velocity ΔV(t) is large (this meansthat the velocity of the preceding vehicle is lower than that of thevehicle), it is desirable for the vehicle to reach to the targetinter-vehicle distance L_(T)(t) from the present actual inter-vehicledistance L (t) as quickly as possible as shown in FIG. 11. Hence, insuch a situation as described above, the first gain fL by which thetarget inter-vehicle deviation {L_(T)(t)−L(t)} in the inter-vehicledistance feedback control system is multiplied is increased but thesecond gain fv by which the target relative velocity deviation{ΔV_(T)(t)−ΔV(t)} is multiplied is reduced.

With the response characteristic in the inter-vehicle distance feedbackcontrol system increased, thus, the follow-up characteristic of theactual inter-vehicle distance L(t) to the target inter-vehicle distanceL_(T)(t) is required to be increased.

In the third embodiment, the first and second gains fv and fL in theinter-vehicle distance feedback control system are set in accordancewith the relative velocity ΔV(t) of the vehicle to the preceding vehicleΔV(t) to achieve the optimum inter-vehicle distance control response tostart the smooth follow-up run to the preceding vehicle in spite of themagnitude of the relative velocity ΔV(t).

FIG. 14 shows the functional block diagram of the automatic vehicularvelocity control apparatus in the third embodiment according to thepresent invention.

The preceding vehicle follow-up run controller 80(5) functionallyincludes the inter-vehicle distance command value calculating section801, the target inter-vehicle distance calculating section 802, the gaindetermining section 803, and the vehicular velocity command valuecalculating section 804. The preceding vehicle follow-up run controller80(5) receives the inter-vehicle distance L and the relative velocity ΔVfrom the inter-vehicle distance sensor 1 and the vehicular velocity Vfrom the vehicular velocity sensor 2.

If the preceding vehicle cannot be recognized by means of theinter-vehicle distance sensor 1, the vehicular velocity set as thetarget vehicle speed is outputted to the vehicular velocity controlsection 4 as the command value V*(t) of the vehicular velocity.

The inter-vehicle distance command value calculating section 801calculates the command value of the inter-vehicle distance in thefollowing equation (11) on the basis of the vehicular velocity V(t) andthe relative velocity to the preceding vehicle ΔV(t) if the precedingvehicle is recognized by means of the inter-vehicle distance sensor 1.

L*(t)=a·{V(t)+ΔV(t)}+Lof  (11A).

V(t)+ΔV(t)=Vt(t)  (11B).

In the equations (11A) and (11B), Vt(t) denotes the vehicular velocityof the preceding vehicle. It is noted that the command value of theinter-vehicle distance L*(t) may be derived in accordance with thefollowing equation (12) on the basis of only the vehicular velocity V(t)as follows:

L*(t)=a′V(t)+Lof′  (12).

The target inter-vehicle distance calculating section 802 derives thetarget inter-vehicle distance L_(T)(t) and the target relative velocityΔV_(T)(t) in accordance with the filter processing of an equation (13)of TABLE 4.

In the equation (13) of TABLE 4, ω_(M) and ζ_(M) denote the specificangular frequency and the damping factor to determine the responsecharacteristic of the target inter-vehicle distance L_(T)(t) and thetarget relative velocity ΔV_(T)(t). In either case, a designer sets anarbitrary value therefor.

In the calculation of the equation (13) of TABLE 4, the inter-vehicledistance L0 and the relative velocity ΔV0 immediately after thepreceding vehicle has been recognized are initial values.

If the Laplace transform for the evolved equation of (13) is carriedout, an equation (14) of TABLE 4 is carried out.

The equation (14) of TABLE 4 is the transfer function from the commandvalue L* (t) of the inter-vehicle distance to the target inter-vehicledistance L_(T)(t) and is expressed in the second-order equation.

The gain determining section 803 determines the first gain fL by whichthe target inter-vehicle distance deviation {L_(T)(t)−L(t)} in theinter-vehicle distance feedback control system is multiplied and thesecond gain fv by which the target relative velocity deviation{ΔV_(T)(t)−ΔV(t)} is multiplied according to the relative velocityΔV(t).

First, with the relative velocity ΔV(t) as a parameter, the specificangular frequency ωC and the damping coefficient ζC which are previouslystored in the maps are derived. The specific angular frequency ωC andthe damping factor ζC are the parameters to determine the responsecharacteristic of the inter-vehicle distance feedback control system.

FIG. 14 shows an example of the map representing the specific angularfrequency ωC.

FIG. 15 shows the example of the damping coefficient.

Next, the first gain f_(L) and the second gain fv to calculate thecommand value V*(t) of the vehicular velocity are calculated on thebasis of the specific angular velocity ωC and the damping coefficient ζCas shown in equations (15A) and (15B).

fL=ωC²/ωnV  (15A)

and

fv=1−2ζcωc/ωnV  (15B)

In the equation (15A), ωnV denotes the specific angular frequency in theinter-vehicle distance control system so as to make the detected valueof the vehicular velocity (actual vehicular velocity) V(t) equal to thecommand value V*(t) of the vehicular velocity. The first gain fL isproportional to a square ωC of the specific angular frequency in theinter-vehicle distance feedback control system and the second gain fv isproportional to the specific angular frequency ωC. Hence, when therelative velocity ΔV(t) is varied, the first gain f_(L) is largelyvaried than the second gain fv.

The vehicular velocity command value calculating section 804 calculatesthe command value V*(t) of the vehicular velocity to make the relativevelocity ΔV(t) equal to the target relative velocity ΔV(t) andsimultaneously to make the inter-vehicle distance L(t) equal to thetarget inter-vehicle distance L_(T)(t).

That is to say, the first gain fL and the second gain fv determined bythe gain determining section 803 according to the relative velocityΔV(t) are used to calculate the command value of the vehicular velocityin accordance with an equation (16).

V*(t)={V(t)+ΔV(t)}−{fv{ΔV_(T)(t)−ΔV(t)}+f_(L){L_(T)(t)−L(t)}  (16).

The vehicular velocity control section 4 is the same as that describedin each previous embodiment, namely, adjustably controls at least one oreach of the throttle actuator 30, the automatic actuator 60, and/or theA/T gear ratio actuator 40 in order that the actual vehicular velocityV(t) is made equal to the command value V*(t) of the vehicular velocity.

As appreciated from the equation (15), as the specific angular frequencyωc in the inter-vehicle distance feedback control system becomes large,the first gain fL by which the target inter-vehicle distance deviation{L_(T)(t)−L(t)} in the equation (16) is multiplied becomes large and thesecond gain by which the target relative velocity deviation{ΔV_(T)(t)−ΔV(t)} is multiplied becomes small. Since the specificangular frequency ωc is set to be a larger value as the relativevelocity ΔV(t) becomes large as shown in FIG. 15, the first gain fLbecomes large but the second gain fv becomes small as the relativevelocity value ΔV(t) becomes large.

Hence, in the situation where the vehicle is approaching to thepreceding vehicle whose relative velocity ΔV(t) is high (large) as shownin FIG. 11, the target inter-vehicle distance deviation {L_(T)(t)−L(t)}is feedback to a large degree and the target relative velocity deviation{L_(T)(t)−ΔV(t)} is feedback to a small degree.

In other words, even if the target inter-vehicle distance deviation{L_(T)(t)−L(t)} is small, the command value V*(t) of the vehicularvelocity is largely varied so that the response characteristic in theinter-vehicle distance control system becomes fast.

At this time, in addition, the command value V*(t) of the vehicularvelocity is not largely varied even if the target relative velocitydeviation {αV_(T)(t)−ΔV(t)} is large. No abrupt deceleration is carriedout even if the relative velocity ΔV(t) is large (high).

Hence, in the situation of FIG. 11 where the vehicle follows up thepreceding vehicle whose relative velocity is large, a slow decelerationof the vehicle but a quick arrival at the target inter-vehicle distancecan be achieved to provide the feeling of relief for the vehicularoccupant(s).

On the other hand, since a small value is set to be the specific angularvelocity ωc in the inter-vehicle distance feedback control system as therelative velocity ΔV(t) becomes small (low), the first gain fL by whichthe target inter-vehicle distance deviation {L_(T)(t)−L(t)} in theequation (16) is multiplied becomes reduced but the second gain fv bywhich the target relative velocity deviation {ΔV_(T)(t)−ΔV(t)} ismultiplied becomes increased.

Hence, in the situation where the vehicle follows up the precedingvehicle whose relative velocity ΔV(t) is small as shown in FIGS. 12 and13, the target inter-vehicle distance deviation {L_(T)(t)−L(t)} isfeedback to a small degree in the calculation of the command value V*(t)in the equation (16) and the target relative velocity deviation{ΔV_(T)(t)−ΔV(t)} is feedback to a large degree.

In other words, although the target inter-vehicle distance deviation{L_(T)(t)−L(t)} is large, the command value V*(t) is not largely variedand the response characteristic in the distance feedback control systembecomes slow.

It is noted that, at this time, even if the target relative velocitydeviation {ΔV_(T)(t)−ΔV(t)) is largely feedback, the relative velocityΔV(t) itself is so small that the command value V*(t) of the vehicularvelocity is not so largely varied and the abrupt deceleration is notcarried out. Hence, in the situation where the vehicle follows up thepreceding vehicle whose relative velocity ΔV(t) is small, no abruptdeceleration is carried out and the inter-vehicle distance can slowly beexpanded.

In addition, such the abrupt deceleration as to give the vehicular rundisagreeable to the vehicular occupant(s) in the case of the comparativeexample does not occur.

It is noted that the hardware structure of the automatic vehicularcontrol apparatus in the third embodiment is the same as that shown inFIGS. 1A and 1B.

(Fourth Embodiment)

In the third embodiment, the first gain fL by which the targetinter-vehicle distance deviation {L_(T)(t)−L(t)} is multiplied isincreased to improve the response characteristic in the inter-vehicledistance feedback control system to make the actual inter-vehicledistance L(t) equal to the target inter-vehicle distance L_(T)(t).However, there is a trade-off relationship such that the increase in thefirst gain fL causes the decrease in the stability in the system.

In a fourth embodiment of the automatic vehicular velocity controlapparatus, the feedforward loop is added to the inter-vehicle distancefeedback control system so as to provide the desired targetinter-vehicle distance response characteristic from the inter-vehicledistance command value L*(T). The compensated command value Vc of thevehicular velocity corrects the command value of the vehicular velocityV*(t) derived by the inter-vehicle distance feedback control system.

Thus, the inter-vehicle distance feedback control system can improve theresponse characteristic without sacrifice of the stability.

FIG. 17A shows the functional block diagram of the automatic vehicularvelocity control apparatus in the fourth embodiment.

It is noted that the same reference numerals shown in FIG. 17A as thosein FIG. 14 correspond to like elements in the third embodiment shown inFIG. 14 and the detailed explanations thereof are omitted herein.

The preceding vehicle follow-up run controller 800A(5) shown in FIG. 17Aincludes the pre-compensated vehicular velocity command calculatingsection 805 and the corrected vehicular velocity command valuecalculating section 806.

The pre-compensated vehicular velocity command value calculating section805 calculates the compensated vehicular velocity command value Vc bycarrying out the filtering process of an equation (17) of TABLE 4.

The filter expressed in the equation (17) of TABLE 4 is represented bythe product between the inverse of the transfer function from thevehicular velocity command value V*(t) to the actual inter-vehicledistance L(t) and the responsive characteristic of the targetinter-vehicle distance L_(T)(t) shown in the equation (14).

It is noted that the transfer function from the command value V*(t) ofthe vehicular velocity up to the actual inter-vehicle distance L(t) isrepresented by the product between the transfer function Gv(s) (refer tothe equation (1)) in the vehicular velocity control system into whichthe command value V*(t) of the vehicular velocity is inputted and fromwhich the actual vehicular velocity V(t) is outputted and the differencebetween the actual vehicular velocity V_(T)(t) of the preceding vehicle,i.e., the integrator to integrate the relative velocity to achieve theactual inter-vehicle distance L(t). It is noted that the initial valuesto calculate the actual inter-vehicle distance L(t) are theinter-vehicle distance L0 and the relative velocity ΔV0 immediatelyafter the vehicle has just been recognized the preceding vehicle.

The corrected vehicular velocity command value calculating section 806adds the compensated vehicular velocity command value V*(t) calculatedin the inter-vehicle distance feedback control system to derive thecorrected command value V*′ (t) of the vehicular velocity.

V*′(t)=V_(T)(t)−V*(t)−Vc  (18).

The vehicular velocity control section 4 adjustably controls at leastone of the throttle actuator 30, the automatic brake actuator 60, theA/T gear ratio actuator 40 to make the actual vehicular velocity equalto the corrected command value V*′(t).

FIGS. 18A, 18B, 18C, 18D, 19A, 19B, 19C, 19D, 20A, 20B, 20C, and 20Dshow the results of simulations in a case where the vehicle whosevehicular velocity was V=90 Km/h, the vehicular velocity V_(T) of thepreceding vehicle was 60 Km/h, and the vehicle has recognized thepresence of the preceding vehicle at the inter-vehicle distance of 120m, and the vehicle has started to follow up the preceding vehicle.

FIGS. 18A through 18D show the results of simulations of theinter-vehicle distance, the vehicular velocity, the relative velocity,and the accelerations in the automatic vehicular velocity controlapparatus in either of the first or the second embodiment when thespecific angular frequency ωc was lowered.

FIGS. 19A through 19D show those results of simulations thereof in acase where the specific angular frequency is lowered.

FIGS. 20A through 20D show those results of simulations thereof in eachof the third and fourth embodiments. In FIGS. 18A through 20D, eachsolid line denotes the target value and the broken line denotes theactual value.

In a case wherein the vehicle follows up the preceding vehicle whoserelative velocity value ΔV(t) is large, the response in theinter-vehicle distance control system is quickened with the specificangular frequency in each of the first and second embodiments increased.

As shown in FIGS. 18A through 18D, the large variation in thedeceleration occurs after the preceding vehicle follow-up run startalthough the actual inter-vehicle distance L(t) is made coincident withthe target inter-vehicle distance L_(T)(t).

In addition, if the response in the inter-vehicle distance controlsystem is made slow with the specific angular frequency lowered in eachof the first and second embodiments, the variation in the decelerationbecomes moderate as shown in FIGS. 19A through 19D but the actualinter-vehicle distance L(t) largely overshoot the target inter-vehicledistance L_(T)(t). This gives the vehicular occupant(s) a feel ofanxiety.

However, in each of the third and fourth embodiments, even if thevehicle follows up the preceding vehicle whose relative velocity ΔV(t)is large (high), the actual vehicular velocity L(t) is varied in such amanner as to be made substantially coincident with the targetinter-vehicle distance L_(T)(t) as shown in FIGS. 20A through 20D and noremarkable variation in the acceleration (deceleration) occurs after thepreceding vehicle follow-up run start.

FIGS. 21A, 21B, 21C, 21D, 22A, 22B, 22C, 22D, 23A, 23B, 23C, and 23Dshow the results of the simulations when the preceding vehicle whoserelative velocity was ΔV=60 Km/h was recognized at the inter-vehicledistance of 70 m during the vehicular run at V=74 Km/h.

FIGS. 21A through 21D show the results of simulations when the specificangular frequency in the inter-vehicle distance feedback control systemin each of the first and second preferred embodiments is increased.

FIGS. 22A through 22D show the results of simulations when the specificangular frequency in the inter-vehicle distance feedback control systemin each of the first and second preferred embodiments is lowered.

FIGS. 23A through 23D show the results of simulations when each of thethird and fourth embodiments is operated.

In FIGS. 21A through 23D, the solid line denotes the target value andthe broken line denotes the actual value.

In a case where the vehicle follows up the preceding vehicle whoserelative velocity is small (low), the response in the inter-vehicledistance control system is quickened with the specific angular frequencyincreased in either of the first or second embodiment. At this time,although the actual inter-vehicle distance L(t) is varied in such amanner as to be made substantially coincident with the targetinter-vehicle distance L_(T)(t) as shown in FIGS. 21A through 21D butthe large deceleration variation occurs after the follow-up run start.

It is noted that in the case where the response in the inter-vehicledistance control system is made slow with the specific angular frequencyin either of the first or second embodiment lowered, the actualinter-vehicle distance L(t) is varied in such a manner as to be madesubstantially coincident with the target inter-vehicle distance L_(T)(t)and moderate variation in the deceleration occurs.

It is noted that in a case where the response characteristic in theinter-vehicle distance control system is made slow with the specificangular frequency increased and with the response in the inter-vehicledistance control system quickened in each of the first and secondpreferred embodiments, the actual inter-vehicle distance L(t) is variedin such a manner as to be substantially made coincident with the targetinter-vehicle distance L_(T)(t) and the variation in the decelerationbecomes moderate.

In a case where the vehicle follows up the preceding vehicle whoserelative velocity ΔV(t) is small (low) in each of the third and fourthpreferred embodiments, the actual inter-vehicle distance L(t) is variedin such a manner as to be substantially made coincident with the targetinter-vehicle distance L_(T)(t) and no large variation in thedeceleration occurs after the start of the follow-up run.

As described above, since the first gain fL by which the targetinter-vehicle distance deviation {L_(T)(t)−L(t) } in the inter-vehicledistance feedback control system is multiplied and the second gain fv bywhich the target relative velocity deviation {ΔV_(T)(t)−ΔV(t)} in theinter-vehicle distance feedback control system is multiplied are set inaccordance with the relative velocity ΔV(t), the optimum inter-vehiclecontrol response characteristic can be achieved in various precedingvehicle follow-up run situations. No large variation occurs after thestart of the preceding vehicle follow-up run.

In addition, since the first gain fL by which the target inter-vehicledistance deviation {L_(T)(t)−L(t)} is multiplied is increased, theresponse in the inter-vehicle distance control system becomes fast, thefollow-up capability of the actual inter-vehicle distance to the targetinter-vehicle distance L_(T)(T) can be raised.

In a case where the vehicle follows up the preceding vehicle whoserelative velocity ΔV(t) is large, a quick arrival to the targetinter-vehicle distance ΔV_(T)(t) can be achieved and the feeling of thedisburden can be given to the vehicular occupant(s).

In addition, in the automatic vehicular velocity control apparatusaccording to the present invention, the response characteristic can beincreased without sacrifice of the stability in the inter-vehicledistance feedback control system.

It is noted that since, in each of the third and fourth embodiments, thefirst gain fL by which the target inter-vehicle distance feedbackcontrol system is multiplied and the second gain fv by which the targetrelative velocity deviation (ΔV_(T)(t)−ΔV(t)} in the above-describedcontrol system is multiplied are set in accordance with the relativevelocity ΔV(t).

Only the first gain fL by which the target inter-vehicle distancedeviation {L_(T)(t)−L(t)} in the inter-vehicle distance feedback controlsystem may be set in accordance with the relative velocity ΔV(t) and thecommand value V*(t) of the vehicular velocity may be calculated bysubtracting the target inter-vehicle distance deviation fL{L_(T)(t)−L(t)} multiplied by the first gain fL from the vehicularvelocity of the preceding vehicle V_(T)(t) (=V(t)+ΔV(t)).

FIG. 17B shows an alternative of the fourth preferred embodiment of theautomatic vehicular velocity control apparatus according to the presentinvention.

As shown in FIG. 17B, the coefficients determining section 502corresponds to the maps shown in TABLE 1 and TABLE 2 and shown in FIG. 3and the target inter-vehicle distance calculating section 810 having thetransfer function expressed as ω_(M) ²/(s²+2ζ_(M)ωs+ω_(M) ²) derives thetarget inter-vehicle distance L* (or L_(T)) and the target relativevelocity ΔV* (or ΔV_(T)).

The vehicular velocity command value calculating section 820 includes: afirst subtractor D_(L) to subtract the target inter-vehicle distance L*from the actual inter-vehicle distance L to derive the targetinter-vehicle distance deviation (L*−L, namely, {L_(T)(t)−L(t)}); asecond subtractor Dv to subtract the target relative velocity ΔV* fromthe actual relative velocity ΔV to derive the target relative velocitydeviation (ΔV*−ΔV, namely, {ΔV_(T)(t)−ΔV(t)}); a first multiplier havingthe first gain fL by which the subtraction result is multiplied toderive fL×(L*−L); a second multiplier having the second gain fv by whichthe subtraction result is multiplied to derive fv×(ΔV*−ΔV); a summer S1to add the vehicular velocity V to the relative velocity ΔV and subtractfL×(L*−L)+fv×(ΔV*−ΔV) from the added result of (V+ΔV) to output(V+ΔV)−{fL×(L*−L)+fv×(ΔV*−ΔV)} (this calculation is the same as theequation (16)) as the target vehicular velocity V*; and an adder S2 toadd the summed result from the summer S1 to the compensated commandvalue Vc of the vehicular velocity command value calculating section 850to derive the final command value V*′ of the vehicular velocity(V*′=V_(T)−V*−Vc). The pre-compensated vehicular velocity command valuecalculating section 850 has the transfer function as given by ω_(M)²s(s+ωv)/ωv(s²+2ζ_(M)ω_(M)s+ω_(m) ²). The individual numerical values ofthe specific angular frequency ω_(M) and the damping factor ζM arederived from the maps 502 according to the relative velocity ΔV and theinter-vehicle distance deviation ΔL.

Each of the numerical values of ωM and ζM is previously distributed intothe maps in accordance with the signed values of the inter-vehicledistance deviation ΔL and of the relative velocity ΔV of the vehicle tothe preceding vehicle.

In FIG. 17B, the numerical values of each of the specific angularfrequency ωM and the damping factor ζM are previously stored in a firstquadrant of the respective maps to cope with the situation (I mode) inwhich the relative velocity ΔV is positively large and the inter-vehicledistance deviation ΔL is positively large such that the vehicle has madethe traffic lane change to overtake the old preceding vehicle and hasfollowed up the new preceding vehicle whose relative velocity islarge(as shown in FIG. 13), are previously stored in a second quadrantof the respective maps to cope with the situation (II mode) in which therelative velocity ΔV is negatively small and the inter-vehicle distancedeviation ΔL is negatively small such that the other vehicle isinterrupted into the same traffic lane as the vehicle as the interruptvehicle (as shown in FIG. 12), and are previously stored in a fourthquadrant (III mode) in which the relative velocity ΔV is positive andthe inter-vehicle distance deviation ΔV is negative such that the newpreceding vehicle whose relative velocity is large is recognized at theovertake traffic lane to which the vehicle has made the traffic lanechange.

It is noted that a symbol of s denotes a Laplace transform operator andthe relative velocity which is large means that the velocity of thepreceding vehicle is lower than that of the vehicle and that therelative velocity is large in the negative direction (since ΔV=Vt−V).

It is noted that an inter-vehicle distance (feedback) control systemdefined in the appended claims includes the inter-vehicle distancesensor 1; the vehicular velocity sensor 2; the inter-vehicle distancecommand calculating section 501 (801); the coefficients determiningsection 502; the target inter-vehicle distance calculating section 503(802); and the vehicular velocity command value calculating section 504(803, 804) in each of the first, second, third, and fourth embodimentsand includes the sections 810 and 820 shown in FIG. 17B and thevehicular velocity control system includes the vehicular velocitycontrol section 4 and the vehicular velocity sensor 2 in eachembodiment.

It is also noted that the comparative example described in thespecification is the previously proposed automatic vehicular velocitycontrol apparatus described in the Japanese Patent ApplicationPublication No. Heisei 11-59222 published on Mar. 12, 1999.

The entire contents of Japanese Patent Applications Heisei 10-240180(filed in Japan on Aug. 26, 1998) and Heisei 11-166828 (filed in Japanon Jun. 14, 1999) are incorporated herein by reference.

Although the present invention has been described by reference tocertain embodiments described above, the present invention is notlimited to the embodiments described above. Modifications and variationsof the embodiments will occur to those skilled in the art in light ofthe above teachings.

The scope of the present invention is defined with reference to thefollowing claims.

TABLE 1 Relative Inter-Vehicle Distance Deviation (Actual Inter-VehicleDistance - Target Inter-Vehicle Distance) m Velocity −20 −16 −12 −8 −4 04 8 12 16 20 30 40 60 80 100 km/h m/s ζ_(M) MAP −101 −28 0.800 0.8000.800 0.800 0.900 0.950 0.980 0.910 0.653 0.525 0.448 0.317 0.252 0.1680.126 0.101 −86.4 −24 0.800 0.800 0.800 0.800 0.900 0.950 0.984 0.8100.580 0.465 0.396 0.280 0.222 0.148 0.111 0.089 −72 −20 0.800 0.8000.800 0.800 0.900 0.950 0.980 0.700 0.500 0.400 0.340 0.240 0.190 0.1270.095 0.076 −57.6 −16 0.800 0.800 0.800 0.800 0.900 0.880 0.840 0.5800.413 0.330 0.280 0.197 0.156 0.104 0.078 0.062 −43.2 −12 0.800 0.8000.800 0.800 0.900 0.720 0.780 0.450 0.320 0.255 0.216 0.152 0.120 0.0800.060 0.048 −36 −10 0.700 0.700 0.750 0.800 0.800 0.750 0.800 0.3880.275 0.219 0.185 0.130 0.103 0.068 0.051 0.041 −28.8 −8 0.600 0.6000.650 0.700 0.750 0.650 0.720 0.320 0.227 0.180 0.152 0.107 0.084 0.0560.042 0.034 −21.6 −6 0.500 0.500 0.550 0.600 0.650 0.550 0.540 0.2480.175 0.139 0.117 0.082 0.065 0.043 0.032 0.026 −14.4 −4 0.400 0.4000.450 0.500 0.550 0.450 0.360 0.170 0.120 0.095 0.080 0.056 0.044 0.0290.022 0.018 −10.8 −3 0.300 0.300 0.350 0.400 0.400 0.350 0.270 0.1310.093 0.073 0.062 0.043 0.033 0.022 0.017 0.013 −7.2 −2 0.200 0.2000.250 0.300 0.300 0.250 0.180 0.090 0.063 0.050 0.042 0.029 0.022 0.0150.011 0.009 0 0 0.100 0.100 0.150 0.200 0.250 0.900 0.400 0.250 0.2000.100 0.100 0.100 0.100 0.100 0.100 0.100 7.2 2 0.046 0.055 0.070 0.1000.180 0.900 0.500 0.350 0.300 0.200 0.200 0.200 0.200 0.200 0.200 0.20010.8 3 0.066 0.079 0.100 0.143 0.255 0.900 0.600 0.450 0.400 0.300 0.3000.300 0.300 0.300 0.300 0.300 14.4 4 0.084 0.100 0.127 0.180 0.320 0.9000.700 0.550 0.500 0.400 0.400 0.400 0.400 0.400 0.400 0.400 18 5 0.1000.119 0.150 0.213 0.375 0.900 0.800 0.650 0.600 0.500 0.500 0.500 0.5000.500 0.500 0.500

TABLE 2 Relative Inter-Vehicle Distance Deviation (Actual Inter-VehicleDistance - Target Inter-Vehicle Distance) m Velocity −20 −16 −12 −8 −4 04 8 12 16 20 30 40 60 80 100 km/h m/s ω_(M) MAP −101 −28 0.130 0.1200.110 0.100 0.110 0.110 0.070 0.130 0.140 0.150 0.160 0.170 0.180 0.1800.180 0.180 −86.4 −24 0.140 0.130 0.120 0.110 0.110 0.110 0.082 0.1350.145 0.155 0.165 0.175 0.185 0.185 0.185 0.185 −72 −20 0.150 0.1400.130 0.120 0.110 0.110 0.098 0.140 0.150 0.160 0.170 0.180 0.190 0.1900.190 0.190 −57.6 −16 0.160 0.150 0.140 0.130 0.120 0.110 0.105 0.1450.155 0.165 0.175 0.185 0.195 0.195 0.195 0.195 −43.2 −12 0.180 0.1600.150 0.150 0.140 0.140 0.130 0.150 0.160 0.170 0.180 0.190 0.200 0.2000.200 0.200 −36 −10 0.180 0.180 0.160 0.180 0.170 0.160 0.160 0.1550.165 0.175 0.185 0.195 0.205 0.205 0.205 0.205 −28.8 −8 0.190 0.1800.180 0.180 0.180 0.180 0.180 0.160 0.170 0.180 0.190 0.200 0.210 0.2100.210 0.210 −21.6 −6 0.200 0.190 0.180 0.180 0.180 0.180 0.180 0.1650.175 0.185 0.195 0.205 0.215 0.215 0.215 0.215 −14.4 −4 0.210 0.2000.180 0.180 0.180 0.180 0.180 0.170 0.180 0.190 0.200 0.210 0.220 0.2200.220 0.220 −10.8 −3 0.210 0.210 0.190 0.190 0.185 0.180 0.180 0.1750.185 0.195 0.205 0.215 0.220 0.220 0.220 0.220 −7.2 −2 0.220 0.2100.200 0.200 0.180 0.180 0.180 0.180 0.190 0.200 0.210 0.220 0.220 0.2200.220 0.220 0 0 0.230 0.220 0.210 0.200 0.180 0.180 0.180 0.180 0.1900.200 0.210 0.220 0.220 0.220 0.220 0.220 7.2 2 0.230 0.220 0.210 0.2000.180 0.180 0.180 0.180 0.190 0.200 0.210 0.220 0.220 0.220 0.220 0.22010.8 3 0.220 0.210 0.200 0.190 0.170 0.175 0.180 0.180 0.190 0.200 0.2100.220 0.220 0.220 0.220 0.220 14.4 4 0.210 0.200 0.190 0.180 0.160 0.1700.180 0.180 0.190 0.200 0.210 0.220 0.220 0.220 0.220 0.220 18 5 0.2000.190 0.180 0.170 0.150 0.165 0.180 0.180 0.190 0.200 0.210 0.220 0.2200.220 0.220 0.220

TABLE 3 ${{Gv}(s)} = \frac{\omega v}{s + {\omega v}}$

(1) ${\frac{}{t}\begin{bmatrix}{L_{T}(t)} \\{{\Delta V}_{T}(t)}\end{bmatrix}} = {{\begin{bmatrix}0 & 1 \\{- {\omega_{M}}^{2}} & {{- 2}\zeta_{M}\omega_{M}}\end{bmatrix}\begin{bmatrix}{L_{T}(t)} \\{{\Delta V}_{T}(t)}\end{bmatrix}} + {\begin{bmatrix}0 \\{\omega_{M}}^{2}\end{bmatrix}L*(t)}}$

(6)$\frac{L_{T}(s)}{L*(s)} = \frac{{\omega_{M}}^{2}}{s^{2} + {2\zeta_{M}\omega_{M}s} + {\omega_{M}}^{2}}$

(7)${{Gc}(s)} = {\frac{{Vc}(s)}{L*(s)} = \frac{{\omega_{M}}^{2}{s\left( {s + {\omega v}} \right)}}{{\omega v}\left( {s^{2} + {2\zeta_{M}\omega_{M}s} + {\omega_{M}}^{2}} \right)}}$

(9)

TABLE 4 ${\frac{}{t}\begin{bmatrix}{L_{T}(t)} \\{{\Delta V}_{T}(t)}\end{bmatrix}} = {{\begin{bmatrix}0 & 1 \\{- {\omega_{M}}^{2}} & {{- 2}\zeta_{M}\omega_{M}}\end{bmatrix}\begin{bmatrix}{L_{T}(t)} \\{{\Delta V}_{T}(t)}\end{bmatrix}} + {\begin{bmatrix}0 \\{\omega_{M}}^{2}\end{bmatrix}L*(t)}}$

(13)$\frac{L_{T}(s)}{L*(s)} = \frac{{\omega_{M}}^{2}}{s^{2} + {2\zeta_{M}\omega_{M}s} + {\omega_{M}}^{2}}$

(14)${{Gc}(s)} = {\frac{{Vc}(s)}{L*(s)} = \frac{{\omega_{M}}^{2}{s\left( {s + {\omega v}} \right)}}{{\omega v}\left( {s^{2} + {2\zeta_{M}\omega_{M}s} + {\omega_{M}}^{2}} \right)}}$

(17)

What is claimed is:
 1. An automatic vehicular velocity control apparatusfor an automotive vehicle, comprising: an inter-vehicle distancedetector to detect an inter-vehicle distance from the vehicle to apreceding vehicle which is running ahead of the vehicle; a vehicularvelocity detector to detect a vehicular velocity of the vehicle; arelative velocity detector to detect a relative velocity of thepreceding vehicle to the vehicle; an inter-vehicle distance commandvalue calculator to calculate a command value of the Inter-vehicledistance; a control response characteristic determinator to determine acontrol response characteristic of an inter-vehicle distance controlsystem the control response characteristic determinator comprising atleast one parameter to determine the control response characteristic ofthe inter-vehicle distance control system the parameter being determinedaccording to at least the detected value of the relative velocity; avehicular velocity command value calculator to calculate a command valueof the vehicular velocity according to a detected value of the vehicularvelocity, the detected value of the relative velocity, a first deviationbetween the command value of the inter-vehicle distance and a detectedvalue thereof, a second deviation between a target value of the relativevelocity and the detected value thereof, a first gain to be multipliedby the first deviation, and a second gain to be multiplied by the seconddeviation; and a vehicular velocity control section to control at leastone of a driving force of the vehicle, a braking force of the vehicle,and a gear ratio of a vehicular transmission in such a manner that adetected value of the vehicular velocity is made equal to the commandvalue of the vehicular velocity.
 2. An automatic vehicular velocitycontrol apparatus for an automotive vehicle as claimed in claim 1,wherein the control response characteristic determinator includes amemory in which a plurality of control modes and control responsecharacteristics corresponding to the respective control modes arepreviously stored on the basis of signs and magnitudes of the firstdeviation and of the detected value of the relative velocity.
 3. Anautomatic vehicular velocity control apparatus for an automotive vehicleas claimed in claim 2, wherein the memory includes two-dimensional arrayhaving a longitudinal axis of the deviation and a lateral axis of thedetected value of the relative velocity each of which a parameter todetermine the control response characteristic is previously stored. 4.An automatic vehicular velocity control apparatus for an automotivevehicle as claimed in claim 3, wherein the parameter comprises aspecific angular frequency and a damping factor in a second ordertransfer function.
 5. An automatic vehicular velocity control apparatusfor an automotive vehicle as claimed in claim 4, wherein theinter-vehicle distance control system includes a target value calculatorto calculate a target value of the inter-vehicle distance and a targetvalue of the relative velocity from the inter-vehicle distance commandvalue using a first filter prescribed by the specific angular frequencyω_(M) and the damping factor ζ_(M) selected from the memory and thevehicular velocity command value calculator calculates the vehicularvelocity command value on the basis of the detected values of theinter-vehicle distance, the relative velocity, and the vehicularvelocity and the target values of the inter-vehicle distance and therelative velocity.
 6. An automatic vehicular velocity control apparatusfor an automotive vehicle as claimed in claim 5, wherein the firstfilter is a second order filter.
 7. An automatic vehicular velocitycontrol apparatus for an automotive vehicle as claimed in claim 6,wherein a transfer function of the second order filter is expressed asω_(M) ²/(s²+2ζ_(M)ω_(M)s+ω_(M) ²), wherein s denotes a Laplace transformoperator.
 8. An automatic vehicular velocity control apparatus for anautomotive vehicle as claimed in claim 7, further comprising: acorrection value calculator to calculate a correction value for thevehicular velocity command value calculated by the vehicular velocitycommand value calculator using a second filter having a transferfunction prescribed by the transfer function of the first filter, aninverse of a transfer function of the vehicular velocity control system,and an integration element; and a vehicular velocity command valuecorrection section to correct the vehicular velocity command value usingthe correction value calculated by the correction value calculator. 9.An automatic vehicular velocity control apparatus for an automotivevehicle as claimed in claim 1, wherein the first gain and the secondgain are determined according to the parameter, the first gain and thesecond gain being varied according to the detected value of the relativevelocity.
 10. An automatic vehicular velocity control apparatus for anautomotive vehicle, comprising: an inter-vehicle distance detector todetect an inter-vehicle distance from the vehicle to a preceding vehiclewhich is running ahead of the vehicle; a vehicular velocity detector todetect a vehicular velocity of the vehicle; a relative velocity detectorto detect a relative velocity of the preceding vehicle to the vehicle;an inter-vehicle distance command value calculator to calculate acommand value of the inter-vehicle distance; a control responsecharacteristic determinator to determine a control responsecharacteristic of an inter-vehicle distance control system in accordancewith to a deviation between the command value of the inter-vehicledistance and a detected value thereof and a detected value of therelative velocity; a vehicular velocity command value calculator tocalculate a command value of the vehicular velocity on the basis of thedetermined control response characteristic of the inter-vehicle distancecontrol system; a vehicular velocity control section to control at leastone of a driving force of the vehicle, a braking force of the vehicle,and a gear ratio of a vehicular transmission in such a manner that adetected value of the vehicular velocity is made equal to the commandvalue of the vehicular velocity, wherein the control responsecharacteristic determinator includes a memory in which a plurality ofcontrol modes and control response characteristics corresponding to therespective control modes are previously stored on the basis of signs andmagnitudes of the deviation and of the detected value of the relativevelocity, the memory includes two-dimensional arrays, eachtwo-dimensional array having a longitudinal axis of the deviation and alateral axis of the detected value of the relative velocity each ofwhich a coefficient to determine the control response characteristic ispreviously stored, each coefficient to determine the control responsecharacteristic is a specific angular frequency {overscore (ω)}_(M) and adamping factor ζ_(M) of the inter-vehicle distance control system, theinter-vehicle distance control system includes a target value calculatorto calculate a target value of the inter-vehicle distance and a targetvalue of the relative velocity from the inter-vehicle distance commandvalue using a first filter prescribed by the specific angular frequency{overscore (ω)}_(M) and the damping factor ζ_(M) selected from thememory and the vehicular velocity command value calculator calculatesthe vehicular velocity command value on the basis of the detected valuesof the inter-vehicle distance, the relative velocity, and the vehicularvelocity and the target values of the inter-vehicle distance and therelative velocity, the first filter is a second order filter, and atransfer function of the second order filter is expressed as ({overscore(ω)}_(M) ²/(S²+2ζ_(M){overscore (ω)}_(M)s+{overscore (ω)}_(M) ²), with sdenoting a Laplace transform operator; the automatic vehicular velocitycontrol apparatus for an automotive vehicle further comprising: acorrection value calculator to calculate a correction value for thevehicular velocity command value calculated by the vehicular velocitycommand value calculator using a second filter having a transferfunction prescribed by the transfer function of the first filter, aninverse of a transfer function of the vehicular velocity control system,and an integration element; and a vehicular velocity command valuecorrection section to correct the vehicular velocity command value usingthe correction value calculated by the correction value calculator,wherein the transfer function of the second filter is expressed as{overscore (ω)}_(M) ²s(s+{overscore (ω)}v)/{overscore (ω)}v(s²(s²+2ζ{overscore (ω)}_(M)s+{overscore (ω)}_(M)s+{overscore (ω)}_(M) ²),with {overscore (ω)}v denoting a break point angular frequency in avehicular velocity control system constituted by the vehicular velocitycontrol section.
 11. An automatic vehicular velocity control apparatusor an automotive vehicle as claimed in claim 10, wherein the correctionvalue calculator is a feedforward system connected between the controlresponse characteristic determinator and the vehicular velocity commandvalue calculator.
 12. An automatic vehicular velocity control apparatusfor an automotive vehicle as claimed in claim 1, wherein the relativevelocity detector comprises a differentiator to differentiate thedetected value of the inter-vehicle distance.